Recently, white light emitting LEDs (“white LEDs”) have become more popular and more commonly used to replace conventional fluorescent, compact fluorescent and incandescent light sources. White LEDs generally include one or more photoluminescence materials (typically inorganic phosphor materials), which absorb a portion of the radiation emitted by the LED and re-emit light of a different color (wavelength). The phosphor material may be provided as a layer on, or incorporated within a wavelength conversion component that is located remotely from the LED. Typically, the LED generates blue light and the phosphor(s) absorbs a percentage of the blue light and re-emits yellow, green, or a combination of green and yellow light. The portion of the blue light generated by the LED that is not absorbed by the phosphor material combined with the light emitted by the phosphor provides light which appears to the eye as being white in color.
To generate white light with a higher CRI (Ra), that is 80 or higher, it is known to additionally include red and/or orange light emitting phosphors in the wavelength conversion component. The inclusion of orange and red phosphors can also be beneficial where it is required to generate “warm white” light, that is light with a lower CCT (Correlated Color Temperature), for example warm white light with a CCT of 2700K to 3000K. Whilst such arrangements are capable of producing light with the required characteristics, the very high cost of orange and/or red phosphors makes such arrangements prohibitively expensive for many applications. A need exists therefore for an inexpensive solution for generating high CRI color light and/or light with lower CCTs.
The present invention arose in an endeavor to at least in part overcome the drawbacks of the conventional photoluminescence wavelength conversion components.